Don't love the wife but just can't leave

My name is Matt and and I have been married to Emma for 4 years now (been together for 12 yrs). Basically, I don't think I love my wife, but I can't leave because she falls to pieces when I try telling her i'm unhappy and want a divorce. I think most women would agree to split after hearing how unhappy I am, but Emma is determined to hang in there no matter what. She says she loves me and that im her 'entire world' - which makes me feel incredibly guilty and I can't bare to see her so distressed. A BRIEF HISTORY For several months I felt very uncomfortable seeing Emma whilst she was still in another relationship (of 6yrs), she tells me she's 'unhappy' and stuff. I didn't know she was seeing anyone else at first and a bit surprised of such 'attention' from a 'non-single' girl (although we were just friends at this stage, I was still attracted to her and emotionally attached). I tried saying several times that 'I can't do this' - meaning seeing someone who is with someone else. Eventually, I meant it and said I couldn't see her anymore under this predicament. Not long after this, I got a phone call from Emma telling me she's now single - alas! I was so excited I wanted to jump for joy. I drove round straight away, I was so happy, I felt like a man should feel on his wedding day. When I got there, Emma opened the door, the look on her face was of sadness - I was confused and hurt. She didn't seem to share my enthusiasm or happiness and I instantly felt like I'd arrived at someone's funeral. My heart sank inside like a deflated balloon. This isn't what I expected or wanted. I suggested she should have time to herself (to think, recharge her batteries etc) and then we could meet again and be joyous together. But no, this wasn't an option for Emma, and snapped at me saying that I was 'showing my true colours now!' by suggesting such a thing. It's as though she thought I wanted to 'dump her' and this gave rise to her anger. This wasn't true, I merely wanted her to release some baggage as she looked to be on the rebound. I wanted us to come together and be happy together. For the next few months, (or years really) things were and are still difficult. It was easy for Emma to snap at me (and I suppose, I let her - not knowing how to respond, or too scared to). I think i've just been tolerating her most of the time and not really loving her. I think i loved her in the beginning (before I realised the full extent of her moods) I didnt realise she was such a fiery person with a very short fuse. We did go to 'Relate' for marriage counseling 2 yrs ago and she did begin to listen to my side of things and calm down a bit. So then we had a baby (now almost 1 yr old). Her moods got worse again and now she's trying stress hypnotherapy - which is all very well, but now I'm thinking that its too late because I don't feel in my heart that I can go back. I can't relate or warm to a 'fiery' person, it's just not in my nature. Even if a fiery person had a so called 'good week' - it doesn't matter, they'd still be the same fiery person and someone whom I could never warm towards. They'd still have the same personality which I don't like or love. I could never love such a personality like this. Because this is who I am and I can never change. I know, I may shun love in this relationship. I know there are things that I could do to be more loving, but I can't because it doesn't feel right for me, I cannot love a fiery person, i'd just be living a lie. Am I a perfectionist ? Am I a naive idealist - looking for a perfect soulmate? Why can't I just forgive her and try again? I dont know. But I do know that I don't fancy her and I don't even like her kissing me. Yes, I do think there could be a soulmate out there for me, but I just want to be with someone calm and who I can have a conversation with and not feel like im treading on egg shells all the time. Having a baby now has made things difficult because i don't she would be of a 'stable nature' if i left.